kexec or similar for FreeBSD

[Matthew Jacob]

Hi Russell!

Yes, I think it is. Solaris supports something like this and the idea here 
is that with complicated I/O subsystems it's too hard to get them and 
locks cleaned up in a crash, but you want to get all the forensics you 
can, so doing a jump to a preloaded kernel that has a small and separate 
running address space seems a good way to go.

If I were doing this, I'd try and set up the alternate kernel to be in the 
same state it would be just after the loader has prelinked all the pieces 
together. So, you run along in the loader, and jump to the kernel where 
all the pieces are linked together. Perhaps you could extend the loader to 
preload/prelink the alternate kernel as well (or just copy and relocate 
the main kernel).

On Thu, 16 Jun 2011, Russell Cattelan wrote:

> I have been contacted about possibly implementing a fast reboot
> mechanism for FreeBSD similar to kexec on Linux.
>
> I have just started looking into how this accomplished so I figured
> a note to freebsd hackers would also be a good place to ask
> for comments.
>
> Has anybody looked at doing something like kexec?
>
> Is it the right thing to do for FreeBSD.  I'm concerned that the way
> FreeBSD handles early kernel modules (loaded via the boot loader)
> vs linux which does everything via initrd is going to be a problem.
>
> Thanks for any help on this.
>
> -Russell Cattelan
>
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